Conventionally, a trigger switch for hand-held electric power tools, as illustrated in FIG. 4, consisted of a switch unit having a push-button member 4 projecting out of a case 3, and a trigger member 1 pivotally supported by the case 3 by means of a pivot shaft 2 and adapted to bear upon the push-button member 4 when it is actuated or, in other words, pulled by a finger. According to this structure, since the push-button member 4 projects out of the case 3, and the trigger member 1 acts upon the free end of the push-button member 4, it has been difficult to achieve a compact design of the trigger switch. Also, the need for a push-button switch means a high cost not only for the component parts themselves but also for assembling them. Furthermore, since the push-button member moves into and out of the case, it has been difficult to achieve a satisfactory sealing of the switch mechanism which is coupled to the push-button member. Additionally, the use of such a push-button mechanism requires a relatively large force to be applied to the trigger member for its operation.